Many methods have been explored for regulating ionic current. Recently, experimental demonstrations have shown that the ionic current through a uniformly surface-charged ionic channel can be modulated by the gate voltage applied on the channel. However, due to the native surface charge on the walls of the channel, the design requires high gate voltages and it is very difficult to completely turn off the ionic current. A “bipolar” ionic transistor by chemically modulating the surface charge of the nanochannel. It was demonstrated that the ionic current was completely off in this bipolar ionic transistor. But this bipolar ionic transistor is a “passive” transistor, with no active electrical gate control.
A need exists for an electrical gate on a surface-charge modulated ionic channel, wherein by applying a gate voltage on the electrical gate, one can turn on the ionic current.